Components and optical assemblies with hollow structures

Abstract

The present invention relates to a structural component, particularly an optical element (Mi) or a structural component, comprising a body (25) including a hollow structure (27) through which a fluid (28) can flow and which has a plurality of cooling channels (31), a fluid distribution section (33), and a fluid recovery section (31), wherein the fluid distribution section (33) includes a connecting channel (33b) leading to a common inlet channel (33a) connected to an inlet opening (29) for supplying fluid (28) to the cooling channels (31), and / or the fluid recovery section includes a connecting channel leading to a common outlet channel connected to an outlet opening for discharging fluid (28) from the cooling channels (31). According to one aspect of the present invention, the inlet channel (33a) has a flow cross-section (A) decreasing from a connecting channel (33b') adjacent to the inlet opening (29), and / or the outlet channel has a flow cross-section decreasing from a connecting channel adjacent to the outlet opening.

Description

[Technical Field]

[0001] [Reference to related applications] This application claims priority to German Patent Application No. 102023205652.6 of 16 June 2023, which incorporates its full disclosure by reference.

[0002] The present invention relates to a structural component, particularly an optical element or structural component, comprising a body including a hollow structure through which a fluid can flow and having a plurality of cooling channels, a fluid distribution section, and a fluid recovery section, wherein the fluid distribution section includes a connecting channel leading to a common inlet channel connected to an inlet opening for supplying fluid to the cooling channels, and / or the fluid recovery section includes a connecting channel leading to a common outlet channel connected to an outlet opening for discharging fluid from the cooling channels. The present invention also relates to an optical device, particularly a lithography system, comprising at least one such component. [Background technology]

[0003] Current lithography systems are equipped with a cooling system that includes a cooling circuit for thermal stabilization of components such as optical elements or structural components. The cooling lines of the cooling circuit can pass through both the body of the optical element and the body of the structural component in the form of a hollow structure. To ensure the highest possible heat dissipation and good controllability of the cooling system (low latency and high precision), a fluid, usually in the form of a coolant, is flowed through the body of the component being cooled, or more precisely, through their hollow structure (active cooling). In many cases, water is used as the coolant because it has a large heat capacity and is very readily available compared to other fluids. The flowing fluid also improves heat transfer at the surface through which the fluid passes (forced convection), and in the process, the time constant of the thermal system is reduced.

[0004] Momentum exchange occurs in the flow boundary layer between the fluid and the component walls. In laminar and steady flow, a constant force acts on the component through which the flow passes (loss of fluid pressure). When the flow velocity exceeds a critical velocity (critical Reynolds number Re; e.g., Re=2300 in pipe flow), which depends on local geometric boundary conditions and inflow and outflow boundary conditions, the viscosity of the fluid can no longer dampen small turbulences, and the turbulence causes sustained periodic and random fluctuations in the flow (turbulence). This turbulence increases momentum transport from the flow to the body and can undesirably accelerate the component in the form of fluid-induced oscillations (FIV), even at frequencies that are controllable depending on the geometry, medium, and flow (e.g., frequencies used for controlling mirror position).

[0005] Therefore, flow-induced oscillations arise as a result of pressure and momentum fluctuations excited by turbulence in the fluid flow, and the resulting forces on the walls of the hollow structure or cooling channel lead to dynamic excitation of the component. Furthermore, up to 10% of the hydrodynamic fluctuations (turbulence) are coupled to the output side as acoustic pressure waves, which can propagate upstream at the speed of sound of the cooling fluid and accumulate at resonant frequencies (like organ pipes) depending on the geometric shape of the cooling circuit. Attempts have been made to minimize the occurrence of flow-induced oscillations by optimizing flow induction and keeping the flow velocity as low as possible.

[0006] A problem that arises when optimizing fluid flow guidance through hollow structures is that these structures are typically fabricated using standard manufacturing methods (grinding, milling, drilling, etc.). Due to manufacturing limitations, such methods often result in geometric shapes that are not ideal for flow in terms of turbulence generation, acoustics, and resulting force excitation. This also affects the fluid distribution and fluid recovery sections.

[0007] Generally, the fluid distribution unit and the fluid recovery unit are arranged spatially apart from each other. The fluid distribution unit distributes the fluid flow or fluid from the inlet opening to multiple cooling channels, and the fluid recovery unit collects the fluid flow from the multiple cooling channels and returns it to the outlet opening. For this purpose, the fluid distribution unit and the fluid recovery unit have multiple branching points where the fluid is distributed to the cooling channels. The fluid distribution unit and / or the fluid recovery unit may have branching points that form a tree structure. In the case of a tree structure, at least one of the multiple branches formed at the first branching point is further divided into two or more branches at the second branching point. In the components described herein, the fluid distribution unit includes connecting channels to connect the cooling channels or groups of two or more cooling channels to the inlet channel connected to the inlet opening, and / or the fluid recovery unit includes connecting channels to connect the cooling channels or groups of two or more cooling channels to the outlet channel connected to the outlet opening.

[0008] Inlet and outlet channels typically have a cylindrical cavity shape because such cavities can be easily manufactured by milling or drilling. Patent Document 1 describes a mirror for a lithography system equipped with a fluid distribution section in the form of an inlet channel and a fluid recovery section in the form of an outlet channel, where these channels take the form of cylindrical holes. In this case, the connecting channels referred to as the distribution channel / recovery channel in Patent Document 1 open perpendicular to the inlet or outlet channel, respectively, and are similarly manufactured in the form of holes. The hollow structure design described in the above document is manufactured by conventional manufacturing methods and is not optimized for minimizing turbulence formation.

[0009] However, especially for components used in EUV lithography systems, only minimal flow-induced vibrations can be tolerated. In such cases, the maximum allowable force generated by flow-induced vibrations is typically on the order of mN to μN. [Prior art documents] [Patent Documents]

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] The problem addressed by the present invention is to provide a component and an optical device having at least one such component that reduces the occurrence of flow-induced vibration.

Means for Solving the Problems

[0012] According to a first aspect, this problem is solved by the inlet channel having a flow cross-section that decreases (in the longitudinal direction of the inlet channel) from a connection channel adjacent to the inlet opening and / or the outlet channel having a flow cross-section that decreases (in the longitudinal direction of the outlet channel) from a connection channel adjacent to the outlet opening.

[0013] For simplicity, in the following, the hollow structure is assumed to be symmetrical with respect to the fluid distribution section and the fluid recovery section, i.e., the fluid distribution section and the fluid recovery section have the same geometric shape. Therefore, in the following, only the fluid recovery section or inlet channel will be described, and the description of the fluid distribution section will apply to the fluid recovery section as appropriate. However, this is not always the case; in principle, the fluid distribution section and the fluid recovery section may have different geometric shapes optimized for their respective flow conditions (e.g., flow direction, swirl, expansion / contraction, etc.). Since the flow conditions in the fluid distribution section and the fluid recovery section differ greatly due to their different functions, it may be advantageous for them to have different geometric shapes. The fluid distribution section distributes fluid between the cooling channels, and this process should be as uniform and turbulent as possible. The fluid recovery section recovers fluid. As the fluid flows from the small-diameter cooling channels to the connecting channels approximately perpendicular to the cooling channels, and from each connecting channel to the outlet channel of the fluid recovery section, turbulence, i.e., FIV-affected flow, may occur due to abrupt changes in diameter and shear. Therefore, the design solutions for the fluid recovery section may need to differ from those for the fluid distribution section.

[0014] In the inventors' view, a cylindrical inlet channel is undesirable from the viewpoint of generating turbulence or flow-induced oscillations in the fluid recovery section. Since multiple connecting channels, each receiving a portion of the volumetric flow rate, branch sequentially from the inlet channel in the longitudinal direction of the inlet channel, the volumetric flow rate in the inlet channel decreases from the connecting channels adjacent to the inlet opening in the longitudinal direction of the inlet channel. This decrease in volumetric flow rate can lead to flow separation in the inlet channel, which in turn can lead to turbulence and / or periodic fluctuations (an exponential gradient of flow velocity in the inlet channel). Turbulence can also be formed in the connecting channels leading to the inlet channel.

[0015] Therefore, to reduce the generation of turbulence, it is proposed to adapt the flow cross-section of the inlet channel (or outlet channel) to the decrease in velocity (and pressure gradient). It is not necessary for the flow cross-section to decrease strictly monotonically over the entire length of the inlet or outlet channel. Within the scope of this application, the decrease in flow cross-section is understood to mean that the inlet channel (or outlet channel) may also have sections with a constant flow cross-section. However, overall, the flow cross-section of the inlet or outlet channel decreases from the adjacent connecting channel toward the end of the inlet channel (or outlet channel).

[0016] Reducing the flow cross-section can be achieved in different ways from a manufacturing perspective. Conventional manufacturing methods, such as milling or drilling, can be used to reduce the flow cross-section. However, from a manufacturing perspective, the geometric shapes of hollow structures that can be fabricated are very limited (see above). It is also possible to realize inlet channels with reduced flow cross-sections using novel alternative manufacturing methods other than standard machining methods (grinding, milling, drilling, etc.). In principle, virtually any desired, and sometimes complex, geometric shape of a hollow structure can be formed in the body using alternative manufacturing methods. Therefore, hollow structures optimized with respect to fluid flow and flow-induced vibrations can be realized using alternative manufacturing methods. For example, alternative manufacturing methods may include selective laser etching or back-side laser ablation.

[0017] In selective laser etching, light in the form of ultra-edge pulsed laser radiation (ps or fs pulses) is focused onto a volume of a transparent workpiece or body. In this case, the pulse energy is absorbed only within the focal volume as a result of a multiphoton process. Within the focal volume, the optical and chemical properties of the transparent material change, either without cracking or possibly with microcracks, making it selectively etchable. By shifting the focal volume within the material, a continuous volume region is modified, which can then be removed by wet chemical etching. In wet chemical etching, the body is usually immersed in the etching solution for several weeks or months, and the etching solution preferably (selectively) removes the modified material. As described in International Publication No. 2021 / 115643, for example, as a result of shifting the focal volume within the workpiece, it is theoretically possible to fabricate a hollow structure of a desired geometric shape using selective laser etching.

[0018] In back-side laser ablation, light in the form of ultrashort pulse laser radiation (ps or rs pulses) is similarly focused onto the volume of a transparent workpiece or body. Unlike selective laser etching, the body material is directly removed by correspondingly high pulse energy to create a hollow structure. Like selective laser etching, back-side laser ablation utilizes the fact that materials in the form of conventional glass, such as quartz glass, borosilicate glass, or titanium-doped quartz glass (ULE®), are transparent to laser radiation in the visible light (VIS) to near-infrared wavelength range. Energy can be imparted to the material by multiphoton absorption only when the intensity of the laser pulse is sufficiently high. As a result, the laser pulse can be focused onto the back of the material with virtually no loss or distortion, so that the laser pulse is absorbed only in the region near the focal point on the back, and material removal can be performed.

[0019] Methods for removing material from the back surface of a workpiece or body by laser ablation are described, for example, in the papers "Three-dimensional hole drilling of silica glass from the rear surface with femtosecond laser pulses" (Y. Li et al., Optics Letters Vol. 26(23), pages 1912-1914 (2001)), "Precision glass machining, drilling and profile cutting by short pulse lasers" (S. Nikumb et al., Thin Solid Films, Vol. 477(1-2), pages 216-221 (2005)), or "Water-assisted femtosecond laser ablation for fabricating three-dimensional microfluidic chips" (Yan Li, Shiliang Qu, Current Applied Physics, Vol. 13, Issue 7, 2013, pages 1292-1295).

[0020] Depending on the manufacturing method used, the reduction in the flow cross-section can be achieved gradually (in some cases, as in conventional manufacturing methods) or continuously, and this can be achieved by alternative manufacturing methods, or in some cases, by conventional manufacturing methods.

[0021] Preferably, the flow cross-section of the inlet channel decreases linearly in the longitudinal direction of the inlet channel, and / or the flow cross-section of the outlet channel decreases linearly in the longitudinal direction of the outlet channel. It is preferable that the flow cross-section of the inlet channel decreases linearly in the longitudinal direction from the inlet opening to approximate a substantially constant decrease in the fluid velocity in the longitudinal direction of the inlet channel due to the presence of connecting channels leading to the inlet channel. Such a linear decrease is preferable because the volume flow rate decreases in stages as a portion of the volume flow rate branches off from the inlet channel in each distribution channel.

[0022] The linear decrease of the longitudinal flow cross-section of the inlet channel corresponds to at least the number of connecting channels at a plurality of positions y in the longitudinal direction y of the inlet channel i for which the associated flow cross-section A i (y i ) satisfies a linear equation, i.e., it is understood that the following equation holds A i (y i ) = A0 - const.y i

[0023] The linear decrease of the longitudinal flow cross-section of the inlet channel can be continuous or stepped (see below). In the first case, the inlet channel has no irregularities in the flow cross-section. In this case, the above equation can be satisfied at all positions in the longitudinal direction of the inlet channel. However, it is also possible for the above equation to be satisfied only for a plurality of positions that do not necessarily correspond to, for example, the number of connecting channels, in which case each position y i is associated with one of the connecting channels. Between these positions y i the flow cross-section deviates (slightly) from the above equation in this case. Within the scope of the meaning of the present application, the longitudinal direction of the inlet channel is understood to mean the line along which the transition between the connecting channel and the inlet channel runs on the peripheral wall of the inlet channel. Therefore, the longitudinal direction is not the direction in which the center of the flow cross-section of the inlet channel is located

[0024] i is usually associated with the location where each step is positioned

[0025] ​In one embodiment, the inlet channel and / or outlet channel have a flow cross-section that is circular in shape. In the above case where the flow cross-section decreases linearly from the inlet / outlet opening, the decrease in the flow cross-section A can be directly represented by its radius R, i.e., the flow cross-section A is R 2 It is proportional to, i.e., A∝R 2 The following holds true. Therefore, a parabolic (or square root) profile arises with respect to the local radius R in the longitudinal direction of the inlet channel. As described above, there can be a linear or stepwise reduction of the flow cross-section. In particular, the square root profile can be taken only at specific nodes or at multiple locations in the longitudinal direction of the inlet channel, and the square root profile can be approximated by a linearly interpolated interval between these locations. Simulations show that using a circular inlet channel with the linearly decreasing flow cross-section described above results in a 30% to 90% reduction in FIV compared to an inlet channel with a circular flow cross-section and a constant radius R. Therefore, a linear reduction of the flow cross-section enables a significant reduction in flow-induced vibrations. Further reductions in flow-induced vibrations can be achieved by iterative optimization of the flow cross-section profile using the linear reduction of the flow cross-section described here as the initial configuration.

[0026] In yet another embodiment, the inlet channel and / or outlet channel have a rectangular flow section or rectangular cross-sectional portion, preferably with a constant width and a decreasing, particularly linear, height of the rectangular flow section or rectangular cross-sectional portion.

[0027] The longitudinal direction of the connecting channel typically extends into a common plane that also extends into the longitudinal direction of the inlet channel. The width of the rectangular flow section or section portion is measured perpendicular to this plane, and the height of the section is measured within this plane. The constant width of the flow section or section portion prevents abrupt changes in diameter at the transition between the inlet channel and each connecting channel, which would occur if the width of the flow section or section portion also decreased. When the width b of the flow section is constant, for a constant (linear) decrease in the flow section, a particularly simple relationship arises between the flow section A (or its area) and the height h of the flow section in the form of a linear function between area A and height h, i.e., A ∝ R holds (at least at the aforementioned multiple locations in the longitudinal direction of the inlet or outlet channel).

[0028] In principle, the flow cross-section of an inlet or outlet channel can have any geometric shape. In particular, the flow cross-section can consist of two or more cross-sectional portions having a predetermined geometric shape. Such cross-sectional portions may have, for example, the rectangular shape described above.

[0029] In one advanced form of the above embodiment, the inlet channel and / or outlet channel have a flow cross-section consisting of a rectangular cross-section portion and a semicircular cross-section portion. The semicircular cross-section portion is adjacent to the side of the rectangular cross-section portion, which usually has a constant width. In this case, the diameter of the semicircular cross-section portion corresponds to the width of the rectangular cross-section portion. This ensures that the flow cross-section remains constant over the length of the inlet or outlet channel, eliminating abrupt changes in diameter at the transition to the connecting channel. The flow cross-section described herein is advantageous from a manufacturing standpoint and can be realized, for example, by a combination of milling and drilling.

[0030] In yet another embodiment, the inlet channel and / or outlet channel have a flow cross-section that is annular in shape. The annular flow cross-section forms an annular gap, and the reduction in the flow cross-section is achieved by the outer circumference of the annular cross-section being usually constant, and the inner circumference increasing from the connecting channel adjacent to the inlet or outlet opening. The annular flow cross-section may be a round cross-section having an outer radius and an inner radius. However, the annular flow cross-section may be a rectangular ring or a free-form cross-section, provided that the reduction in cross-section can be achieved in a manner suitable for the manufacturing purpose. In this case as well, it is possible to achieve a linear reduction in the longitudinal flow cross-section of the inlet or outlet channel by appropriately selecting the ratio of outer radius to inner radius or outer circumference to inner circumference. The annular flow cross-section is further advantageous because an additional boundary layer is formed in the flow inside the annular gap, which has a stabilizing effect on the flow and reduces the tendency for flow separation.

[0031] An annular flow cross-section can be achieved by removing material in an annular manner from the main body. However, an annular flow cross-section can also be formed by introducing an additional component, for example, a cylindrical inlet channel, which is formed in the shape of a conical rod, and whose cross-section increases with increasing distance from the inlet or outlet opening into which the rod is introduced into the main body. This additional component is fixed to the inlet channel, for example, by being attached to a fluid line or an adapter of the fluid line connected to the inlet opening.

[0032] In yet another embodiment, the opening cross-section of each connection channel in the fluid distribution section decreases sequentially from the connection channel adjacent to the inlet opening, and / or the opening cross-section of each connection channel in the fluid recovery section decreases sequentially from the connection channel adjacent to the outlet opening. This embodiment is particularly preferred in combination with the above embodiment in which the flow cross-section decreases from the connection channel adjacent to the inlet or outlet opening, because in this case, a large abrupt change in cross-section can occur at the transition between the inlet or outlet channel and each connection channel, especially in connection channels that are far from the inlet or outlet channel. To avoid abrupt changes in cross-section and the resulting fluid-induced vibrations, the opening cross-section of each connection channel, more precisely its opening diameter, is made to match the local diameter of the flow cross-section of the inlet or outlet channel at the longitudinal position through which the connection channel passes. To reduce FIV, in this particular case, it is preferable that the flow cross-section of each cooling channel decreases as it moves away from the cooling channel (see below).

[0033] In yet another embodiment, the connecting channel has a flow cross-section that decreases as it moves away from the cooling channel. This embodiment is particularly preferred in combination with the above-described embodiment in which the opening cross-section of the connecting channel changes. In this case, it has been found particularly preferable that the flow cross-section of the connecting channel is not constant but adapted to each opening cross-section.

[0034] In one advanced form of this embodiment, the connecting channel is conical in shape, preferably with an opening angle of less than 8°. In this case, the connecting channel generally has a circular cross-section. The choice of opening angle or flank angle depends on the local flow velocity or local flow profile. Assuming that the flow cross-section of the connecting channel is the same at the transition to the cooling channel, in the above embodiment, where the opening cross-section of the connecting channel decreases as it moves away from the inlet or outlet opening, the opening angle of the connecting channel increases as it moves away from the inlet or outlet opening.

[0035] In yet another embodiment, the flow cross-section of the inlet and / or outlet channels is reduced in steps. As described above, even in the case of a stepwise reduction of the flow cross-section, a linear or constant reduction in cross-section can be approximated. Generally, the more steps there are, the smaller the change in the flow cross-section at each step. To prevent local flow separation, excessively large changes in the flow cross-section (more than 5% of the larger flow cross-section at each step) should be avoided. As described above, each stepwise reducing flow cross-section can be, for example, circular or rectangular, a combination of these two, or annular. While the stepwise reduction of the flow cross-section increases expenditure, it makes manufacturing possible or easier using conventional manufacturing methods.

[0036] It is also possible to individually adapt the flow cross-section of the inlet or outlet channel to the respective flow conditions or boundary conditions using methods other than those described above. As mentioned above, it is not essential that the flow cross-sections of the inlet and outlet channels and the connecting channels be circular in shape. In this case, any type of cascading (gradual change) or diameter design that does not maintain a constant flow cross-section over its length can be considered.

[0037] A second aspect of the present invention relates to a component of the type described at the beginning, wherein the inlet channel has a constant flow cross-section and / or the outlet channel has a constant flow cross-section, and at least two of the connecting channels each have different flow cross-sections. To suppress flow separation (as described above) in the inlet or outlet channel due to pressure gradient and volumetric flow rate reduction, the volumetric flow rate discharge from the inlet or outlet channel can also be controlled by the connecting channels. In this case, the back pressure or volumetric flow rate discharge may be affected by the flow cross-section of the connecting channels. Again, the objective is to design the pressure gradient of the inlet or outlet channel to be as constant as possible. Since this depends not only on the static pressure distribution (volumetric flow rate distribution) but also on the dynamic characteristics of the fluid, it is impossible to identify a unique geometric or analytical relationship in the form of a calculation rule in the aspects of the invention described herein. Rather, it is necessary to find the appropriate relationship in this case by iterative approximation (e.g., by simulation).

[0038] In general, in the second aspect of the present invention, interactions may occur in the flow between the inlet or outlet channel and the distribution channel. Note that a smaller cross-section may result in a higher flow velocity. This may lead to increased turbulence and an increased tendency for separation at sharp edges and transitions. These interactions must be considered holistically in order to evaluate the desired positive effects. In the first aspect of the present invention described above, it is possible, and not necessary, for at least two of the connecting channels to have different flow cross-sections; that is, the flow cross-section of the connecting channel may also change when the flow cross-sections of the inlet and outlet channels are reduced.

[0039] In yet another embodiment that can be combined with the first or second aspect of the present invention described above, the flow cross-section of the connecting channels increases sequentially from the connecting channel adjacent to the inlet opening or from the connecting channel adjacent to the outlet opening. The increase in flow cross-section is understood to mean that the flow cross-section of the connecting channel increases over the length of the inlet channel or the entire length of the outlet channel. A connecting channel further from the inlet opening than an adjacent connecting channel has at least the same flow cross-section as that adjacent connecting channel. The connecting channel furthest from the inlet / outlet opening has the largest flow cross-section. As a result of increasing the flow cross-section of the connecting channels, it is possible to achieve an effect similar to decreasing the flow cross-section of the inlet or outlet channel from the inlet or outlet opening. These two measures may be combined with each other, but this is not mandatory. Hereinafter, the flow cross-section of each connecting channel is assumed to be constant. If not, the flow cross-section is generally understood to mean the average cross-section over the length of the connecting channel.

[0040] In yet another embodiment, the flow cross-sections of at least two adjacent connection channels, preferably at least three adjacent connection channels, are of the same size. It is possible to divide the connection channels into groups of adjacent connection channels having the same flow cross-section. For example, such a group may include two, three, or four connection channels. With a proper design, this can result in a FIV reduction of approximately 10% to 50%. The configurations described herein may also potentially form a starting point for simulations to further optimize flow induction. It is also possible to pre-determine the flow cross-sections of each connection channel or all connection channels individually. In particular, all connection channels may each have a different flow cross-section. Crucial here are the geometric pressure loss and dynamic (local) pressure loss occurring within each connection channel, which determine the pressure gradient in the inlet or outlet channel.

[0041] In yet another embodiment, at least one connecting channel has a conical section at the transition to the cooling channel. The conical section allows for flow guidance at the transition to the cooling channel without requiring a sudden change in cross-section. This is particularly preferable when each connecting channel serves to supply fluid to two or more cooling channels, as described in Patent Document 1 cited at the beginning, and the entirety of the above document is incorporated by reference to the content of this application. For this purpose, Patent Document 1 proposes the use of a stepped hole with a larger bore diameter at the transition to the cooling channel. Instead of a large bore diameter section, a conical section is used in this application to avoid the corresponding sudden change in cross-section.

[0042] It is not mandatory for all connecting channels to have a conical section, and the number, dimensions, and position of the conical sections may be varied to prevent flow separation. The conical section is not considered when determining the flow cross-section of the connecting channel as described above. The same dimensional rules as for the conical connecting channel described above apply to the opening angle of the conical section (opening angle < 8°).

[0043] Starting from an ideal but not essential symmetrical basic shape, the overall pressure loss is critically determined by the cooling channels. Assuming that the cooling medium is distributed approximately equally between at least two cooling channels in a parallel structure, the aforementioned changes in the flow cross-section of the inlet or outlet channel and / or connecting channel usually play only a secondary role to the pressure loss and, consequently, the volumetric flow rate through each cooling channel, because the majority of the fluid pressure loss occurs as it flows through the cooling channels themselves. This can be attributed to the fact that the cooling channels have smaller flow cross-sections than the connecting channels and the inlet or outlet channels, and that the pressure loss generally depends on the fourth power of the flow diameter and linearly on the flow length. Therefore, despite the aforementioned changes in the flow cross-section of the inlet or outlet channel and / or distribution channel, the volumetric flow rate is distributed approximately equally among all cooling channels (assuming they themselves have ideal geometric shapes).

[0044] In yet another aspect of the present invention, which can be combined with the first or second aspect in particular, the longitudinal direction of the connecting channel and the longitudinal direction of the inlet channel and / or outlet channel are acute with respect to each other, preferably with an outflow angle of less than 70°.

[0045] As described above, when using conventional manufacturing methods, there are limitations regarding the design of the fluid distribution and fluid recovery sections. The connecting channel and the inlet or outlet channel are usually perpendicular to each other in order to change the direction of flow to a plane parallel to the cooling channel. This results in sharp edges and a limited angular range in which flow separation generally occurs, which increases FIV excitation or FIV contribution. To avoid these sharp edges, it is possible to round them or to try to extend the channels along the tangential radius to each other. To reduce flow-induced vibrations, it is simpler to reduce the outflow angle between the longitudinal direction of the connecting channel and the longitudinal direction of the inlet or outlet channel. The smaller or flatter the outflow angle, the smaller the flow-induced vibrations generally are. The acute outflow angle should be selected to be less than 90° in all cases, and should be as small as possible, close to the optimal value of 0°. In this way, it is possible to reduce flow separation, especially in the connecting channel. The embodiments described herein are advantageous because they can be implemented in both the fluid distribution and fluid recovery sections.

[0046] In yet another aspect of the present invention, which can be combined with the above-described aspects, the distance between the inlet channel and the cooling channel decreases from the connecting channel adjacent to the inlet opening, and / or the distance between the outlet channel and the cooling channel decreases from the cooling channel adjacent to the outlet opening. As a result of the oblique alignment of the inlet or outlet channel with respect to the cooling channel, it is possible to reduce the outflow angle between the longitudinal direction of the connecting channel and the longitudinal direction of the inlet or outlet channel. When both the inlet or outlet channel and the connecting channel are aligned obliquely to the surface of the body from which the cooling channel extends downward, it is possible to form a minimum outflow angle depending on the dimensions of the body. In principle, with respect to the reduction of the outflow angle, it is not important whether only the connecting channel is inclined with respect to the surface or the cooling channel, only the inlet / outlet channel is inclined, or both channel types are inclined at the same time. Further optimization can be achieved by rounding all edges in the flow direction.

[0047] In one embodiment, the body has a first sub-part and a second sub-part rigidly connected to each other along a joint surface, and a hollow structure is formed in at least one of the sub-parts. If the component is an optical element in the form of a mirror, in this embodiment, the body (mirror substrate) is usually first manufactured as a whole, and two or more sub-parts are formed therefrom by machining. Material is removed from at least one of the sub-parts to form a hollow structure or a part of a hollow structure. The two sub-parts are then rigidly connected to each other along a joint surface. To establish the connection, it is possible to use a joining method that can establish the connection without using joining means, such as so-called fusion bonding. The joint surface is planar, but it is also possible for the joint surface to be curved. The substrate may be a material with the smallest possible coefficient of thermal expansion, such as glass ceramic, such as Zerodur®.

[0048] Joining two or more substructures to form the main body may be necessary, especially in the standard manufacturing methods described above, to achieve the complex geometric shapes of the hollow structure. The joining surfaces typically extend perpendicular or substantially perpendicular to the (vertical) plane from which the connecting channels typically extend. This facilitates the manufacturing of the hollow structure by drilling, milling, and / or cutting to (in some cases approximately) realize the above design. It is understood that, when the alternative manufacturing methods described above are used, the main body may also be formed integrally as an alternative.

[0049] When the component is an optical element that reflects radiation in the form of a mirror, the cooling channel generally extends substantially parallel to the reflective surface of the mirror at a relatively small distance from it. To remove the fluid from the reflective surface as quickly as possible, a section of the fluid distribution and fluid recovery section adjacent to the cooling channel is usually arranged substantially perpendicular to the cooling channel, i.e., at an angle of 80° to 100°, and particularly at an angle of about 90°.

[0050] A further aspect of the present invention relates to an optical apparatus, in particular a lithography system, comprising at least one component, in particular an optical element or structural component, designed as described above, and a cooling device designed to flow a cooling fluid through the hollow structure of the main body. The lithography system may be a lithography apparatus for exposing wafers, for example, an EUV lithography apparatus that uses radiation with an operating wavelength in the EUV wavelength range. Alternatively, this may be a different optical apparatus for (EUV) lithography, for example, an EUV inspection system for inspecting masks, wafers, etc., used in EUV lithography. The optical element may be a mirror in the projection system of the EUV lithography apparatus, in particular.

[0051] For example, a cooling system may be designed to circulate a cooling fluid, usually in the form of cooling water, through a cooling channel. For this purpose, the cooling system may optionally have a pump and appropriate supply and discharge lines. The optical system may also be a lithography system for a different wavelength range, such as a DUV wavelength range, such as an EUV lithography system, or an inspection system for inspecting masks, wafers, optical (mirror) elements, etc.

[0052] As described above, a component whose body includes a hollow structure does not necessarily have to be an optical element, but can be a different type of component. For example, the component could be a structural component, for example, in the form of a mount, particularly a frame for mounting an optical element, a frame for mounting a sensor, or in the form of a force frame used in an EUV lithography system, particularly an EUV lithography apparatus. In the case of such a structural component, the body is often formed from a material such as aluminum, steel, ceramic, or SiSiC. The optical device described above may particularly include at least one structural component having a body that includes a hollow structure through which a cooling fluid flows via a cooling device.

[0053] Further features and advantages of the present invention will become apparent from the following description of embodiments of the present invention with reference to the drawings illustrating essential details of the invention, and from the claims. In one variant of the present invention, each feature may be implemented individually, or each or more features may be implemented in any combination.

[0054] An exemplary embodiment is shown in the schematic diagram and described below. [Brief explanation of the drawing]

[0055] [Figure 1] This shows a schematic meridian cross-section of a projection exposure apparatus for EUV projection lithography. [Figure 2] Figure 1 shows a schematic diagram of the mirror body of the projection exposure apparatus, which has a hollow structure including a cooling channel, a fluid recovery section, and a fluid distribution section. [Figure 3]Figure 2 shows a schematic cross-sectional view of the hollow structure of the fluid distribution section, along with an illustration of the turbulent kinetic energy of the fluid as it flows through the fluid distribution section. [Figure 4a] A diagram similar to Figure 3 shows a fluid distribution section including an inlet channel having a circular flow cross-section that decreases in the longitudinal direction. [Figure 4b] A diagram similar to Figure 4a shows a fluid distribution section having a conical connection channel. [Figure 5] This figure shows the relationship between the local diameter of the inlet channel and the maximum diameter of the inlet channel when the flow cross-section decreases linearly in the longitudinal direction of the inlet channel. [Figure 6] Figures similar to Figures 4a and 4b show an inlet channel with a rectangular flow section that decreases in height. [Figure 7a] A diagram of a rectangular flow cross-section is shown. [Figure 7b] The diagram shows a cross-section of the flow path, including both a rectangular and a semicircular section. [Figure 8] A diagram similar to Figure 6 shows how the flow cross-section of the inlet channel decreases in stages. [Figure 9a] A diagram similar to Figure 3 or Figures 7a and 7b is shown, where the inlet channel has an annular flow cross-section. [Figure 9b] A diagram similar to Figure 3 or Figures 7a and 7b is shown, where the inlet channel has an annular flow cross-section. [Figure 10] A diagram similar to Figure 3 is shown, where the inlet channel has a constant flow cross-section, and the flow cross-section of the connecting channel increases as it moves away from the inlet opening. [Figure 11] A diagram similar to Figure 3 is shown, in which the inlet channel has a constant flow cross-section and is arranged with respect to the connecting channel at an acute outflow angle. [Figure 12] A diagram similar to Figure 11 is shown, in which the inlet channel has a flow cross-section that decreases from the inlet opening, and the connecting channel has a flow cross-section that increases from the inlet opening. [Modes for carrying out the invention]

[0056] In the following drawings, identical or functionally identical components shall be referred to by the same reference numeral.

[0057] The essential components of the EUV lithography optical apparatus in the form of microlithography projection exposure apparatus 1 are described below as an example with reference to Figure 1. The description of the basic configuration of projection exposure apparatus 1 and its components should not be understood as limited in this case.

[0058] One embodiment of the illumination system 2 of the projection exposure apparatus 1 includes, in addition to the light source or radiation source 3, an illumination optical unit 4 that illuminates the object field of view 5 on the object surface 6. In an alternative embodiment, the light source 3 may be provided as a module separate from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0059] A reticle 7 positioned in the object field of view 5 is illuminated. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable, particularly in the scanning direction, by a reticle displacement drive 9.

[0060] For illustrative purposes, Figure 1 shows an orthogonal xyz coordinate system. The x-direction extends perpendicular to the plane of the figure. The y-direction extends horizontally, and the z-direction extends vertically. In Figure 1, the scanning direction extends in the y-direction. The z-direction extends perpendicular to the object plane 6.

[0061] The projection exposure apparatus 1 includes a projection system 10. Using the projection system 10, the object field of view 5 is imaged onto the image field of view 11 of the image plane 12. The structure on the reticle 7 is imaged onto the photosensitive layer of the wafer 13, which is positioned in the region of the image field of view 11 of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable, particularly in the y-direction, by a wafer displacement drive 15. On the one hand, the displacement of the reticle 7 by the reticle displacement drive 9, and on the other hand, the displacement of the wafer 13 by the wafer displacement drive 15, can be synchronized.

[0062] Radiation source 3 is an EUV radiation source. Radiation source 3 emits EUV radiation 16, which is also referred to below as the radiation used, illumination radiation, or illumination light. The radiation used has wavelengths in the range of 5 nm to 30 nm. Radiation source 3 may be a plasma source, such as an LPP (laser-generated plasma) source or a GDPP (gas discharge plasma) source. It may also be a synchrotron-based radiation source. Radiation source 3 may be a free electron laser (FEL).

[0063] Illumination radiation 16 emitted from radiation source 3 is focused by a collector mirror 17. The collector mirror 17 may be a collector mirror having one or more elliptical and / or hyperbolic reflecting surfaces. Illumination radiation 16 may be incident on at least one reflecting surface of the collector mirror 17 at an oblique incidence (GI), i.e., at an incidence angle greater than 45°, or at a perpendicular incidence (NI), i.e., at an incidence angle less than 45°. The collector mirror 17 may be structured and / or coated to first optimize its reflectivity for the radiation used, and second to suppress external light.

[0064] Downstream of the collector mirror 17, the illumination radiation 16 propagates through the intermediate focal point of the intermediate focal plane 18. The intermediate focal plane 18 can form a separation between the radiation source module, which includes the radiation source 3 and the collector mirror 17, and the illumination optical unit 4.

[0065] The illumination optical unit 4 comprises a deflection mirror 19 and a first facet mirror 20 located downstream of it in the beam path. The deflection mirror 19 may be a planar deflection mirror or a mirror having a beam influence effect beyond a pure deflection effect. Alternatively or in addition, the deflection mirror 19 may take the form of a spectral filter that separates the wavelength of light used by the illumination radiation 16 from external light of different wavelengths. The first facet mirror 20 includes a plurality of individual first facets 21, also referred to below as field facets. Only a few of these facets 21 are shown as examples in Figure 1. A second facet mirror 22 is located downstream of the first facet mirror 20 in the beam path of the illumination optical unit 4. The second facet mirror 22 includes a plurality of second facets 23.

[0066] Therefore, the illumination optical unit 4 forms a dual facet system. This basic principle is also called a fly-eye integrator. Using the second facet mirror 22, each individual first facet 21 is imaged into the object field of view 5. The second facet mirror 22 is the last beam shaping mirror or, in fact, the final mirror for the illumination radiation 16 in the beam path upstream of the object field of view 5.

[0067] The projection system 10 includes a plurality of mirrors Mi, which are numbered sequentially according to their arrangement in the beam path of the projection exposure apparatus 1.

[0068] In the example shown in Figure 1, the projection system 10 includes six mirrors M1 to M6. Substitution with four, eight, ten, twelve, or any other number of mirrors Mi is equally possible. The second-to-last mirror M5 and the final mirror M6 each have a through aperture for illumination radiation 16. The projection system 10 is a double-shielded optical unit. The projection optical unit 10 has an image-side numerical aperture greater than 0.4 or 0.5, and may be greater than 0.6, for example, 0.7 or 0.75.

[0069] Similar to the mirrors of the illumination optical unit 4, mirror Mi can have a highly reflective coating for illumination radiation 16.

[0070] Figure 2 shows, as an example, the body of the substrate 25 for one of the mirrors Mi in the projection system from Figure 1. In the illustrated example, the material of the substrate 25 is ultra-low expansion glass (ULE®). The substrate 25 can also be formed from a different material having the smallest possible coefficient of thermal expansion, such as glass ceramic, for example, Zerodur®.

[0071] A reflective surface in the form of a reflective coating 26 (see Figure 3) is applied to the surface 25a of the substrate 25. The EUV radiation 16 from the projection system 10 strikes the portion of the surface 25a located within the reflective coating 26, forming an optically usable portion of the reflective coating 26 (not shown herein). To reflect the EUV radiation 16, the reflective coating 26 can have, for example, multiple layer pairs made of materials with different real refractive indices, and the layer pairs can be formed from, for example, Si and Mo when the wavelength of the EUV radiation 16 is 13.5 nm.

[0072] The substrate 25 includes a hollow structure 27 through which a fluid 28, which is cooling water in the illustrated example, can flow. The fluid 28, indicated by the arrows in Figure 2, is introduced into the substrate 25 through a side inlet opening 29 and flows through several cooling channels 31 that form part of the hollow structure 27, thereby cooling the surface 25a of the substrate 25, which is coated with a reflective coating 26.

[0073] To supply fluid 28 to the inlet opening 29 and remove the fluid 28 from the outlet opening 30 of the substrate 25, the projection exposure apparatus 1 is equipped with a temperature control device in the form of a cooling device 32, which is very schematically shown in Figure 1. In the illustrated example, the cooling device 32 serves to supply fluid 28 in the form of cooling water to the hollow structure 27 or the fourth mirror M4, and for this purpose includes a supply line, which is not shown, that is fluid-tightly connected to the inlet opening 29. The cooling device 32 also includes a discharge line (not shown) for removing the cooling water through the outlet opening 30 of the substrate 25 or from the hollow structure 27. The other mirrors M1-M3, M5, M6 of the projection system 10 and the mirrors of the illumination system 2 may also be connected to the cooling device 32 or optionally to further temperature control or cooling devices provided for this purpose for cooling purposes.

[0074] As is clear from Figure 2, the fluid 28 enters a cylindrical inlet channel 33a through an inlet opening 29, which is part of the hollow structure 27 and forms part of the fluid distribution section 33. Multiple (first) connection channels 33b branch off from the inlet channel 33a, each connecting to one of multiple cooling channels 31. In the illustrated example, the cooling channels 31 are positioned at a constant distance of less than approximately 10 mm from the convexly curved surface 25a of the substrate 25. The surface 25a has a convex curvature along a cross-section XZ that extends perpendicular to the Y direction of the XYZ coordinate system. In contrast, the surface 25a is planar along a cross-section YZ that extends perpendicular to the X direction. The cooling channels 31 extend substantially linearly in their longitudinal direction corresponding to the X direction and extend longitudinally over substantially the entire surface 25a of the substrate 25 covered with coating 26. From the cooling channels 31, the fluid 28 flows through multiple (second) connection channels 34b to the cylindrical outlet channel 34a of the fluid recovery section 34. The fluid 28 exits the hollow structure 27 of the substrate 25 through the outlet opening 30 at the end face of the cylindrical outlet channel 34a.

[0075] As is clear from Figure 2, the cooling channel 31 initially extends horizontally (X direction) from the first connection channel 33b or the second connection channel 34b, while the (first and second) connection channels 33b and 34b extend vertically (Z direction). Therefore, the longitudinal axis of the cooling channel 31 at the transition to each of the connection channels 33b and 34b is aligned at a 90° angle with respect to the longitudinal axis of the connection channels 33b and 34b. Such an approximately 90° alignment is typical for the fabrication of the hollow structure 27 on the substrate 25 by the standard processing method described in more detail below.

[0076] To fabricate the hollow structure 27, the substrate 25 shown in Figure 2 is divided into two parts 35a and 35b shown in Figure 3. The upper first part 35a is substantially planar. A reflective surface in the form of a coating 26 is applied to the first part 35a. A substantially larger second part 35b is connected to the first part 35a at a common joint surface 36. Depending on the joining method, for example by fusion, the two parts 35a and 35b can be joined along the joint surface 36. In the illustrated example, the first part 35a and the second part 35b are formed from the same material (ULE®, see above), but it is also possible to form the first part 35a and the second part 35b from different materials.

[0077] The cooling channel 31 is formed by removing material from the first part 35a during the manufacturing of the hollow structure 27, i.e., the cooling channel 31 extends from the joint surface 36 into the first part 35a. The fluid distribution section 33 and the fluid recovery section 34 are formed in the second part 35b by removing material from the second part 35b, i.e., the fluid distribution section 33 and the fluid recovery section 34 extend from the joint surface 36 into the second part 35b. In the case of the hollow structure 27 shown in Figure 2, the material is removed by standard manufacturing methods, more precisely by milling or drilling.

[0078] Figure 3 illustrates the turbulent flow field of the liquid 28 flowing through the fluid distribution section 33, where contours enclosed by dotted or dashed lines represent volume regions of high turbulence or high turbulent kinetic energy. As is clear from Figure 3, high turbulence volume regions occur in both the inlet channel 33a, which has a circular flow cross-section, and the connecting channel 33b, which is also cylindrical. High turbulence volume regions lead to flow-induced oscillations. This is particularly due to the fact that the connecting channel 33b and the inlet channel 33a are aligned at a 90° angle to each other, leading to flow separation, and because the diameters of the connecting channel 33b and the inlet channel 33a are different. In the configuration of the fluid distribution section 33 shown in Figure 3, the design guidelines for low turbulence flow induction are not followed due to limitations in the installation space.

[0079] Even a constant flow cross-section of the cylindrical inlet channel 33a proved undesirable in terms of flow guidance. The volumetric flow rate of the inlet channel 33a decreases from the inlet opening 29 as a portion of it is withdrawn from the inlet channel 33a in each connecting channel 33b, thus reducing the longitudinal (y-direction) flow velocity of the inlet channel 33a. This leads to flow separation, particularly near the end of the inlet channel 33a far from the inlet opening 29, which can in turn lead to turbulence and / or periodic fluctuations (exponential gradient of flow velocity) as shown in Figure 3.

[0080] The following describes how the velocity or pressure gradient of the fluid 28 can be made uniform by adjusting or reducing the cross-sectional area A of the flow cross-section A of the inlet channel 33a in order to prevent separation of the fluid 28 within the inlet channel 33a.

[0081] In the example shown in Figures 4a and 4b, the inlet channel 33a has a flow cross-section A that decreases in the longitudinal direction y of the inlet channel 33a from the connecting channel 33b' adjacent to the inlet opening 29. For clarity, local circular flow cross-sections A in the region of the connecting channel 33b' adjacent to the inlet opening 29 and at the end of the inlet channel 33a far from the inlet opening 29 are shown in Figures 4a and 4b. It is understood that the circular flow cross-section A of the inlet channel 33a extends in the xz plane perpendicular to the longitudinal direction y of the inlet channel 33a, contrary to the illustration in Figures 4a and 4b.

[0082] In the example shown in Figures 4a and 4b, the flow cross-section A decreases linearly in the longitudinal direction y of the inlet channel 33a, which was found to be advantageous for reducing flow-induced vibrations because it keeps the decrease in the axial velocity of the fluid 28 and the decrease in the pressure gradient constant. The flow cross-section A is the diameter squared D 2 or radius squared R 2 Since it is proportional to (A∝R 2 or D 2), for the linear reduction of the flow cross-section A in the longitudinal direction y of the inlet channel 33a, it is necessary to scale the diameter D according to the square root of the distance y from the maximum radius or diameter D0 of the inlet channel, as shown in Figure 5 where the ratio D(y) / D0 is shown as a function of the y coordinate. The numerical values ​​on the horizontal axis of the graph shown in Figure 5 correspond to 12 positions in the longitudinal direction (y direction) of the inlet channel 33a shown in Figure 4a. The curve shown in Figure 5 can be analytically described by the following equation: D(y) / D0 = 0.2887 xy 0.5 .

[0083] Unlike those shown in Figures 4a and 4b, the profile shown in Figure 5 may, in some cases, be approximated by inserting linearly approximated intervals between the 12 locations shown in Figure 4a, i.e., two of the numerical values ​​shown in Figure 5 are connected by straight lines. Such an approximated linear profile may be advantageous from a manufacturing standpoint.

[0084] Similar to the illustration in Figure 3, Figure 4a shows the turbulent kinetic energy of the fluid 28 in the fluid distribution section 33. Based on a comparison of Figure 4a and Figure 3, it is clear that the turbulent kinetic energy of the inlet channel 33a in Figure 4a is significantly reduced compared to that of the inlet channel 33a in Figure 3. When this effect is quantified in terms of its effect on flow-induced oscillations, it can be seen that a reduction of approximately 30% to 90% is possible. Further reduction of flow-induced oscillations can be achieved by further iterative optimization of the flow cross-section A profile in the longitudinal direction y of the inlet channel 33a.

[0085] As is clear from Figure 4a, the flow cross-section A of the inlet channel 33a decreases as it moves away from the inlet opening 29, whereas the diameter or flow cross-section of the connecting channel 33b remains constant in the longitudinal direction y of the inlet channel 33a. This results in a large abrupt change in the cross-section at the transition to each connecting channel 33b near the left end of the inlet channel 33a in Figure 4a. To suppress the local increase in flow-excited vibrations due to the abrupt change in the cross-section, in the example shown in Figure 4b, the opening cross-section M of each connecting channel 33b decreases sequentially starting from the connecting channel 33b' adjacent to the inlet opening 29. The (average) flow cross-section A of the connecting channel 33b decreases as it moves away from the cooling channel 31. V It holds.

[0086] In the example shown in Figure 4b, the connecting channels 33b have a conical shape, and each has an opening angle δ of less than 8°. The opening cross section A of each connecting channel 33b. M Here, if possible, there should be no abrupt change in cross-section at the transition between the inlet channel 33a and each connecting channel 33b, i.e., the opening cross-section A M This is selected so as to be determined by the local diameter D(y) of the inlet channel 33a.

[0087] Figure 6 shows yet another option for linearly reducing the flow section A in the longitudinal direction y of the inlet channel 33a. In the example shown in Figure 6, the flow section A is rectangular and has a height h extending vertically (z direction) and a width b extending laterally with respect to the plane (yz plane) in which the connecting channel 33b and the inlet channel 33a are located (see also Figure 7a). As shown in Figure 6, the width b of the rectangular flow section A is constant in the longitudinal direction y of the inlet channel 33a, but the height h of the rectangular flow section A decreases linearly from the connecting channel 33b' adjacent to the inlet opening 29. Therefore, the flow section A also decreases linearly in the longitudinal direction y of the inlet channel 33a, as it is proportional to the height (A∝h). In the example shown in Figure 6, the relationship between the height h(y) and the y-coordinate in the longitudinal direction y of the inlet channel 33a, with the zero point (arbitrarily) set at the end of the inlet channel 33a away from the inlet opening 29, is as follows. h(y) = h0 + y / L(h E -h0) In the formula, h0 represents the minimum height, h E represents the maximum height, and L represents the length of the inlet channel 33a where the flow cross-section A decreases linearly. If the width b of the flow cross-section A is constant, the problem of abrupt change in cross-section at the transition between the inlet channel 33a and the connecting channel 33b, as explained in relation to Figures 4a and 4b, is solved. Therefore, in the example shown in Figure 6, the connecting channel 33b has a constant circular cross-section A as shown in Figure 6. V It holds.

[0088] The inlet channel 33a does not necessarily need to have a flow cross-section A that decreases along its entire length; the flow cross-section may be constant in, for example, the section of the inlet channel 33a adjacent to the inlet opening 29 and not connected to the connecting channel 33b. For example, this may be advantageous when connecting the inlet channel 33a to a fluid port.

[0089] Instead of the rectangular flow section A shown in Figure 7a, the inlet channel 33a has a rectangular cross-sectional portion A as shown in Figure 7b. R and semicircular cross-sectional portion A K It may have a flow cross-section A consisting of the following. In the case of the flow cross-section A shown in Figure 7b, the rectangular cross-section portion A R The width b is constant, and its height h decreases linearly in the longitudinal direction y of the inlet channel 33a. It is understood that the inlet channel 33 may also have a flow cross-section A with a geometric shape different from those shown in Figures 4a, 4b, and 7a, 7b.

[0090] It is not necessary for the flow cross-section A of the inlet channel 33a to decrease continuously (linearly). Instead, for the rectangular flow cross-section A shown in Figure 6A, the flow cross-section A can decrease in steps or in stages (cascade-like) as shown in Figure 8. Generally, the more steps there are, the smaller the change in flow cross-section A at each step. To prevent local flow separation, excessively large changes in the flow cross-section (more than 5% of the larger flow cross-section at each step) should be avoided. In Figure 8, the flow cross-section A is reduced in relatively large steps for illustrative purposes.

[0091] As an alternative to the rectangular flow cross-section A shown in Figure 8, a progressively decreasing flow cross-section A may have a different geometric shape. While the progressive decrease in flow cross-section A increases expenditure, it allows for the manufacture of the inlet channel 33a using conventional manufacturing methods. Generally, the above-described design of the fluid distribution section 33 is typically fabricated using alternative or novel manufacturing methods, such as selective laser etching or back-side laser ablation.

[0092] In the case of the mirror Mi shown in Figure 9a, the inlet channel 33a has an annular flow section A as shown in Figure 9b. To form the annular flow section A, a ring-shaped piece of material is removed from the body 25 of the mirror Mi, and a frustocone 37 is formed, having a circular cross-sectional area where the radius r increases as it moves away from the inlet opening 29, as is clear from Figure 9a. The outer radius R or outer diameter D of the annular flow section A of the inlet channel 33a thus formed is constant. This creates an annular gap with a flow section A that decreases from the inlet opening 29 or from the connecting channel 33b' adjacent to the inlet opening 29. In the example shown in Figures 9a and 9b, the following equation holds for the annular flow section A. A=π(R 2 -r 2 ) = π(d+b)b = π(Db)b In the formula, b, and therefore the flow cross-section A, also depends on the y-coordinate or longitudinal direction of the inlet channel 33a. In the example shown in Figures 9a and 9b, if the width b(y) is appropriately selected, the flow cross-section A can decrease linearly in the longitudinal direction of the inlet channel 33a.

[0093] The annular flow section A does not necessarily have to be annular and may have a different geometric shape, such as an ellipse, rectangle, oval, or freeform shape. As an alternative to the examples shown in Figures 9a and 9b, the frustocone 37 may not be part of the main body 25 but may be an additional component introduced into and appropriately secured to an inlet channel 33a, which in this case is cylindrical, via an inlet opening 29. In this case, the additional component, which is rod-shaped, may be attached, for example, to a fluid line fastened to and secured therein at the inlet opening 29.

[0094] Figure 10 shows a mirror Mi in which the inlet channel 33a has a constant flow cross-section A, unlike the example described above. In the example shown in Figure 10, the connecting channel 33b has a different flow cross-section A. V It has a flow cross section A of the connecting channel 33b. V As a result of these differences, it is possible to influence the back pressure or volumetric flow rate discharge from the inlet channel 33a in order to keep the pressure gradient in the inlet channel 33a as constant as possible. To achieve this, the flow cross section A of each connecting channel 33b V These can be defined individually. Starting from the connection channel 33b adjacent to the inlet opening 29, the flow cross section A of the connection channel 33b V It was found that an increase in this factor is advantageous for reducing fluid-induced vibrations.

[0095] In the example shown in Figure 10, there are three connecting channels 33b, G1, G2, and G3, and each group has a flow cross-section A V This is achieved because they are the same. Flow section A of the third group G3, which is located adjacent to the entrance opening 29. V In this case, the flow section A of the second group G2. V Smaller, flow cross section A of group 2 G2 V This is the flow cross-section A of the connecting channel 33b of the first group G1. V Smaller.

[0096] Figure 10 clearly shows that the turbulent kinetic energy within the fluid distribution section 33 has been significantly reduced (by approximately 10% to 50%) compared to the conventional fluid distribution section 33 shown in Figure 3. The example shown in Figure 10 can serve as a starting point for iterative optimization of the flow guidance of the fluid distribution section 33, and within that scope, the flow cross-section A V This is defined individually for each connection channel 33b. It is understood that different groupings of connection channels 33b are also possible, for example, each being the same flow section A V It is possible to form four groups, each containing three connection channels 33b having the same characteristics.

[0097] As is also clear from Figure 10, the second and third groups G2 and G3 connecting channels 33b each have a conical section 38 at the transition to the cooling channel 31. The conical section 38 prevents abrupt changes in the cross-section at the transition between each connecting channel 33b and the cooling channel 31. As is clear from Figure 10, each connecting channel 33b is connected to two adjacent cooling channels 31, to which fluid 28 is supplied. The abrupt change in the cross-section at the transition to the cooling channel 31 is due to a flow cross-section A smaller than the y-direction distance between the two adjacent cooling channels 31. V This can be avoided by the conical sections 38 of the connecting channels 33b of the second and third groups G2 and G3, each having such sections. It is understood that the arrangement and configuration of the conical sections 38 may deviate from the configuration shown in Figure 10.

[0098] In the example described above, the connecting channels 33b are arranged vertically (z-direction) and the inlet channel 33a extends horizontally (y-direction), causing the fluid 28 to be deflected by 90° at the opening of the connecting channels 33b, which can lead to flow separation that can cause flow-induced oscillations. To reduce flow-induced oscillations, in the example shown in Figure 11, the longitudinal direction L of the connecting channels 33b is V and the longitudinal direction L of the inlet channel 33a E Between these two points, an acute outflow angle φ of less than approximately 70° is selected. To form the smallest possible outflow angle φ, in the example shown in Figure 11, each connection channel 33b is arranged obliquely to the z direction, and the inlet channel 33a is also positioned at an angle α with respect to the horizontal plane (xy plane). Therefore, in the example shown in Figure 11, the distance D in the z direction between the cooling channel 31 and the inlet channel 33a is selected. Z However, it decreases from the connecting channel 33b' adjacent to the inlet opening 29. Unlike what is shown in Figure 11, the longitudinal direction L of the inlet channel 33a E The connection channel 33b is inclined with respect to the horizontal plane, or in the longitudinal direction L V If it is tilted with respect to the z-direction, it is sufficient to form an acute outflow angle φ.

[0099] Figure 12 shows the three measures described above, namely the reduction of the flow cross-section A of the inlet channel 33a as described in relation to Figures 4a, 4b, 6, and 8, and the reduction of the flow cross-section A of the connecting channel 33b as described in relation to Figure 10. V The Miller Mi is shown, which combines an increase in with the use of an acute outflow angle φ as described in Figure 11. In the design of the fluid distribution section 33 shown in Figure 12, it is necessary to take into account the potential interactions that may occur between the individual measures.

[0100] In the hollow structure 27 described above, it was assumed that the fluid distribution section 33 and the fluid recovery section 34 have the same geometric shape, that is, the description of the fluid distribution section 33 also applies to the fluid recovery section 34. However, in some cases, different dimensions from those of the fluid distribution section 33 may be more advantageous for the fluid recovery section 34, so in principle, it is possible for the fluid distribution section 33 and the fluid recovery section 34 to have different geometric shapes.

[0101] The component in which the main body 25 includes the hollow structure 27 does not necessarily have to be an optical element in the form of a mirror Mi. It could be a different optical element or a non-optical component, such as a structural component of the projection exposure apparatus 1. The component including the main body 25 having the flow-optimized hollow structure 27 can also be used in an optical apparatus different from the projection exposure apparatus 1 described above, such as a lithography apparatus designed for the DUV / VUV wavelength range.

[0102] In general, flow induction can also be improved by rounding the sharp edges of the hollow structure 27, thereby reducing flow-induced vibrations. Introducing radii instead of sharp transitions within the hollow structure 27 also has a beneficial effect in reducing flow-induced vibrations.

Claims

1. Components, particularly optical elements (Mi) or structural components, The device comprises a hollow structure (27) through which a fluid (28) can flow and which has multiple cooling channels (31), a main body (25) including a fluid distribution section (33), and a fluid recovery section (34), In a structural component, the fluid distribution unit (33) includes a connecting channel (33b) leading to a common inlet channel (33a) connected to an inlet opening (29) in order to supply the fluid (28) to the cooling channel (31), and / or the fluid recovery unit (34) includes a connecting channel (34b) leading to a common outlet channel (34a) connected to an outlet opening (30) in order to discharge the fluid (28) from the cooling channel (31), The inlet channel (33a) has a flow cross-section (A) that decreases from the connecting channel (33b') adjacent to the inlet opening (29), and / or The structural component is characterized in that the outlet channel (34a) has a flow cross-section that decreases from the connecting channel adjacent to the outlet opening (30).

2. A component according to claim 1, wherein the flow cross-section (A) of the inlet channel (33a) decreases linearly in the longitudinal direction (y), and / or the flow cross-section of the outlet channel (34a) decreases linearly in the longitudinal direction (y).

3. The component according to claim 1 or 2, wherein the inlet channel (33a) and / or the outlet channel (34a) have a circular flow cross-section (A).

4. In the component according to claim 1 or 2, the inlet channel (33a) and / or the outlet channel (34a) is a rectangular flow cross section (A) or a rectangular cross section portion (A) Ｒ ) has, preferably the rectangular flow section (A) or the rectangular cross-sectional portion (A) Ｒ The width (b) of the rectangular flow section (A) or the rectangular cross section portion (A) is constant, and the width (b) of the rectangular flow section (A) is constant. Ｒ The height (h) of the component decreases, especially linearly.

5. In the component according to claim 4, the inlet channel (33a) and / or the outlet channel (34a) is the rectangular cross-sectional portion (A Ｒ ) and semicircular cross-sectional portion (A Ｋ A component having a flow cross-section (A) consisting of ).

6. The component according to claim 1 or 2, wherein the inlet channel (33a) and / or the outlet channel (34a) have an annular flow cross section (A).

7. In the component according to any one of claims 1 to 6, the opening cross section (A) of each connection channel (33b) of the fluid distribution section (33) Ｍ ) decreases sequentially from the connection channel (33b') adjacent to the inlet opening (29), and / or the opening cross section (A) of each connection channel (34b) of the fluid recovery section (34) Ｍ A component in which the number of elements decreases sequentially from the connection channel (33b) adjacent to the outlet opening (30).

8. In the component according to any one of claims 1 to 7, at least one connection channel (33b, 34b) has a flow cross-section (A) that decreases as it moves away from the cooling channel (31). Ｖ A component that has )

9. The component according to claim 8, wherein at least one connecting channel (33b, 34b) is conical in shape, and preferably the opening angle (δ) of the connecting channel (33b, 34b) is less than 8°.

10. A component according to any one of claims 1 to 9, wherein the flow cross-section (A) of the inlet channel (33a) and / or the outlet channel (34a) decreases in a stepped manner.

11. The component described in the preamble of claim 1, wherein the inlet channel (33a) has a constant flow cross-section (A) and / or the outlet channel (34a) has a constant flow cross-section (A), and at least two of the connecting channels (33b, 34b) each have a different flow cross-section (A Ｖ ).

12. In the component according to any one of claims 1 to 11, the flow cross-section (A) of the connecting channel (33b, 34b) Ｖ The components increase sequentially from the connection channel (33b') adjacent to the inlet opening (29) or the connection channel (34b') adjacent to the outlet opening (30).

13. In the component according to any one of claims 1 to 12, the flow cross-section (A) of at least two adjacent connection channels (33b, 34b), preferably at least three adjacent connection channels. Ｖ ) are components of the same size.

14. A component according to any one of claims 1 to 13, wherein at least one connection channel (33b) has a conical section (38) at the transition to the cooling channel (31).

15. In the component described in the preamble of claim 1, and more particularly in any one of claims 1 to 14, the longitudinal direction (L) of the connection channel (33b) Ｖ ) and the longitudinal direction (L) of the inlet channel (33a) and / or the outlet channel (34a) Ｅ ) are components that form mutually acute angles, preferably with an outflow angle (φ) of less than 70°.

16. In the component described in the preamble of claim 1, and more particularly in any one of claims 1 to 15, the distance between the inlet channel (33a) and the cooling channel (31) is (D Ｚ A component wherein the distance between the outlet channel (34a) and the cooling channel (31) decreases from the connection channel (33b') adjacent to the inlet opening (29), and / or the distance between the outlet channel (34a) and the cooling channel (31) decreases from the connection channel (34b') adjacent to the outlet opening (30).

17. A component according to any one of claims 1 to 16, wherein the body (25) has a first sub-part (35a) and a second sub-part (35b) rigidly connected to each other along a joint surface (36), and the hollow structure (27) is formed in at least one of the sub-parts (35a, 35b).

18. An optical device, particularly a lithography system (1), An optical device comprising at least one component according to any one of claims 1 to 17, in particular an optical mirror (Mi) or a structural component, and a cooling device (32) designed to flow a cooling fluid (28) through a hollow structure (27) of a main body (25).

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